Study Finds Female Stem Cells Are Sturdier

The proof is finally in. Females are better than males. At least that’s the case when it comes to stem cells from females and their ability to regenerate skeletal muscle tissue.

A study by Children’s Hospital of Pittsburgh of UPMC, which was published in the April 9, 2007 issue of the Journal of Cell Biology, is the first ever to report a difference in regenerative capabilities of muscle stem cells based on gender.

This finding could have a major impact on the successful development of stem cells as viable therapies for a variety of diseases and conditions, according to the study’s senior author, Johnny Huard, PhD, director of the Stem Cell Research Center at Children’s and the Henry J. Mankin Professor and Vice Chair for Research in the Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine.

“Regardless of the sex of the host, the implantation of female stem cells led to significantly better skeletal muscle regeneration,” said Dr. Huard, also the deputy director of the McGowan Institute of Regenerative Medicine. “Based on these results, future studies investigating regenerative medicine should consider the sex of the stem cells to be an important factor. Furthermore, investigations such as ours could lead to a better understanding of sex-related differences in aging and disease and could explain, at least partially, the high variability and conflicting results reported in the literature on stem cell biology.”

Dr. Huard’s team made the discovery while working with a population of stem cells they isolated in the lab while searching for a cure for Duchene muscular dystrophy (DMD). DMD is a genetic disease estimated to affect one in every 3,500 boys. Patients with DMD lack dystrophin, a protein that gives muscle cells structure.

Using an animal model of the disease, his laboratory used stem cells to deliver dystrophin to muscles. In his study, Dr. Huard's team injected female and male muscle-derived stem cells into dystrophic mice and then measured the cells’ ability to regenerate dystrophin-expressing muscle fibers. They then calculated the regeneration index (RI). Only one of the 10 male populations of implanted stem cells had an RI over 200. In contrast, 40 percent of the female stem cell populations had an RI higher than 200, and 60 percent of the female populations of stem cells had an RI higher than the mean RI of the male cells (95).“The male cells exhibited increased differentiation after exposure to oxidative stress, which may lead to cell depletion and a proliferative advantage for female cells after cell transplantation,” Dr. Huard said.